N-vinyl lactam polymers are important components in many color sensitive systems including their use as resins for the spinning of fabrics, emulsions for fabric print pastes, dye substantivity additives and other applications where high processing temperatures are employed. These polymers are also useful in cosmetic and pharmaceutical arts where color development as well as unpleasant odors are highly objectionable. A major disadvantage associated with the use of such lactam and other N-vinyl heterocyclic copolymers is their tendency to rapidly yellow or darken upon standing or heating, which problem exists whether or not the heterocyclic vinyl monomer solution as introduced into the polymerization reactor or the alcoholic solution of the corresponding copolymeric product recovered, is initially colorless. Hence it is believed that chromophores or other color forming impurities introduced with the heterocyclic monomer are formed during polymerization and rapidly deteriorate upon standing.
Various proposals to overcome or ameliorate this problem by introducing various stabilizing agents, such as ion exchange resins, absorbants and/or oxidizing agents into the water or aqueous alcohol solutions during, before or after solvent exchange have not proven satisfactory and have not achieved long term water white color stability. Indeed, several stabilizers, optionally used with adjuvants, have additionally imparted an unpleasant odor to the end product or themselves have exhibited corrosive properties owing to acidic pH levels below 4.0, thus introducing further problems, increasing costs and/or limiting the copolymer concentration in many formulations.
Accordingly it is an object of the present invention to overcome the above problems and deficiencies associated with solutions of N-vinyl heterocyclic, particularly N-vinyl lactam copolymers in aqueous solutions.
Another object of the invention is to provide a color stable, odorless solution of an N-vinyl heterocyclic copolymer, which is normally susceptible to discoloration as well as providing an aqueous solution of said copolymers which has long term storage stability and is compatible with components of cosmetic, pharmaceutical and other formulations.
Still another object is to provide the above advantages by a commercially feasible and economically attractive process.
These and many other advantages of the invention will become apparent from the following description and disclosure.